I have been stuck on this for a while cant really see how it works, I have tried drawing it several different ways of doing it. My problem is I can kind of see how it woks in my head but, seem not to be able to put pen do paper. Here Is the question: The van and car eventually reach a steady speed of 18 m s-1 with the rope taut when a child runs out into the road, 30 m in front of the van. The van driver brakes sharply and decelerates uniformly to rest in a distance of 27 m. It takes the driver of the car 1 second to react to the van starting to brake. He then brakes and the car decelerates uniformly at f m s-2, coming to rest before colliding with the van. (c) Find the set of possible values of f. mark scheme: car has (27 + 9) m in which to stop and travels 18 m in first second must stop from 18 m s-1 in 18 m. I can work it out from here no problem simple suvat. I understand the particles will collided if the car aka B travels 36m that I understand, but I cant see how it only needs to travel 18m for a collision to happen. See to me it looks like the mark scheme has ignored the rope between and use it a two separate particles. could someone maybe explain it a different way. I would appreciate if someone could take the time to draw a quick diagram, so I have some sort of intuition. I am really lost on how to approach these sort of questions. p.s like the new layout of physics forum. Big thanks in advance.